The present invention relates to a new and improved construction of sealing system for shutoff elements, which sealing system is of the type embodying two substantially ring-shaped sealing elements, wherein one such sealing element is sealingly connected with the housing or with a closure or blocking element of the shut-off element and the other sealing element is either sealingly connected with the closure element or the housing or is constructed at such itself, and wherein the sealing elements can be pressed against one another by a closing movement of the closure element for carrying out the shutoff action of the shutoff element.
The heretofore known sealing systems for shutoff elements can be essentially divided into two groups, namely, the so-called "hard" seats and those which possess the so-called "soft" seats.
Sealing systems with "hard" seats, i.e. equipped with metal hard-sealing elements, are extensively wear-and-temperature resistant, yet are practically not capable of providing a liquid and gas seal for liquids and gases of low viscosity, additionally they are quite sensitive to contamination or soiling. This is so because both of the sealing elements in the closed or sealing position -- for instance in the case of valves arranged in a radial plane -- have the ring-surfaces bearing against one another and thus contaminants can easily deposit thereat and during the closing movement can become pressed into both seat surfaces. These hard seats additionally are generally welded at the housing seat or closure or blocking element and subsequently machined by grinding.
An appreciably greater gastight seal is provided by sealing systems with "soft" seats, i.e. sealing elements formed of plastic or the like, especially those equipped with a hard and a soft element, because then there can be realized a good mutual fit of both sealing surfaces and contaminants can be pressed into the soft elements and in many instances does not lead to damage. Such "soft" seats, on the other hand, have the drawback that for the soft element there can be only completely or partially used materials formed of organic substances, and which only can be exposed to prescribed operating conditions, especially operating temperatures, which in many instances are much too low.
Attempts have already also been made to improve upon the sealing action of the shutoff element in that there have been constructed sealing systems with multiple seats, so that two or more ring-shaped sealing regions --arranged behind one another-- serve to guarantee the seal. Particlarly in the case of hard seats, where there are present defects in the sealing capability, such multiple seats likewise cannot be constructed to provide a good sealing action because all of the seats must sealingly bear against one another in the same position, and this condition cannot be attained with elements which are practically non-deformable.
There are also known to the art valve constructions equipped with comb-like mutually interengaging thin ring portions formed of metal which are intended to provide a multiple seal in that the thin ring portions of the one element bear with their respective tips, with mutual deformation, at the flanks of an associated ring portion of the other element. Such shutoff elements have been known in this particular field of technology for quite some time, but as a practical matter have not yet been placed into commercial use, presumably because such sealing elements are surely extremely difficult and expensive to manufacture and therefore practically can only come under consideration for special applications.